Electrophotographic copier of image transfer type

ABSTRACT

A coppier includes a cassette comprising a magazine holding a roll of a photosensitive sheet and permitting the withdrawal of a required length of photosensitive sheet from its outlet, a takeup roller for securing the leader end of the photosensitive sheet and for taking up a worm portion of the sheet, a cassette case housing the magazine and the take-up roller, and the photosensitive sheet substantially forming a loop with the cassette case; a drive roller and a tension roller for supporting the loop of photosensitive sheet in the form of an effectively endless belt; and a cassette carrier removably supporting the cassette. The photosensitive sheet extending in effectively endless form is driven back and fourth for charging, exposure and image transfer to copy paper.

United States Patent Tanaka et al.

[ ELECTROPHOTOGRAPHIC COPIER OF IMAGE TRANSFER TYPE [75] Inventors: Susumu Tanaka, Sakai; Yuji Enoguchi, Higashi-Osaka; Takao Fujiwara, Sakai, all of Japan [73] Assignee: Minolta Camera Kabushiki Kaisha,

Osaka, Japan [22] Filed: Feb. 20, 1973 [21] App]. No.: 333,852

[30] Foreign Application Priority Data Mar. 1, 1972 Japan 47-25342 521 US. Cl. "1355/16 [51] Int. Cl G03g 15/22 [58] Field of Search 355/3 R, 16, 72

[56] References Cited UNITED STATES PATENTS 3,588,242 6/l972 Berlier et al. 355/16 3,6l7,l24 ll/l97l Haugen et al 355/16 3,6l9,()50 ll/l97l Swanke 355/]6 Oct. 22, 1974 3,771,866 ll/l973 Masaya Ogawa ..355/l6 Primary ExaminerSamuel S. Matthews Assistant Examiner-Kenneth C. Hutchison Attorney, Agent, or Firm-Welder & Gross [5 7] ABSTRACT A coppier includes a cassette comprising a magazine holding a roll of a photosensitive sheet and permitting the withdrawal of a required length of photosensitive sheet from its outlet, a take-up roller for securing the leader end of the photosensitive sheet and for taking up a worm portion of the sheet, a cassette case housing the magazine and the take-up roller, and the photosensitive sheet substantially forming a loop with the cassette case; a drive roller and a tension roller for supporting the loop of photosensitive sheet in the form of an effectively endless belt; and a cassette carrier removably supporting the cassette. The photosensitive sheet extending in effectively endless form is driven back and fourth for charging, exposure and image transfer to copy paper.

5 Claims, 8 Drawing Figures PATENTEDUET 22 m4 3; 843252 sum 20F a F i g. 4

31 20b 2530 22 32 31 23 E I I a l 3 7 M51 29 M52 M53 PATENTEUum 22 1914 3.843.252 SHEET 30$ 3 BACKGROUND OF THE INVENTION This invention relates to electrophotographic copiers of the powder image transfer type or of the latent image transfer type in which a photosensitive element in the form of a sheet having a photosensitive surface is reciprocally driven to subject the photosensitive element to charging and exposure during the advance of the element to form an electrostatic latent image on the photosensitive surface, after which either a toner is applied to the imagebearing surface to form a visual image or the electrostatic latent image is directly transferred to copy paper at a transfer station, the photosensitive element being repeatedly usable until the photosensitive element per se is fatigued and deteriorated. More particularly, this invention relates to a structure for driving the photosensitive element in copies of the type described which photosensitive element is in the form of a cassette.

Photosensitive elements for electrophotographic copiers of the transfer type heretofore used widely are of the drum or belt type, or may be of the type which comprises a beltv and photosensitive elements adhered to the upper and lower faces of the belt. Such photosensitive element must be replaced along with the drum or belt when it becomes no longer serviceable.

In recent years, a photosensitive sheet of the roll type has been put to use such that when a portion of the photosensitive sheet is fatigued and deteriorated due to repeated use. the deteriorated portion is wound up, permitting a length of fresh photosensitive sheet corresponding to the wound-up amount to be paid out from the roll for use so as to eliminate the trouble of replacing the photosensitive element every time it becomes unserviceable. Thus the sheet of the photosensitive element of the roll type can be used over a prolonged period of time for an increased number of copying cycles. Photosensitive elements of this type are disclosed for example in US. Pat. No. 3,588,242 and Publication of Japanese Pat. application No. 4l356/l97l.

According to the US. Pat. No. 3,588,242, a photosensitive element sheet housed in a drum is pulled out from the drum by a required length, placed along its outer peripheral surface and fixed. When the length of the photosensitive element sheet on the drum surface is deteriorated, the deteriorated portion is wound up into the drum, with a fresh photosensitive portion pulled out from the drum over the outer peripheral surface thereof.

Further, the publication of Japanese Pat. application No. 4i 356/1971 proposes a sheet of photosensitive element wound on a supply shaft, an operative portion of the photosensitive element being placed in a planar fashion between the supply shaft and another shaft for taking up a deteriorated portion of the element. The operative portion of the element is adapted to be driven back and forth along a plane parallel to the surface of a document without permitting the rotation of the shafts.

In the case of the photosensitive element placed around a drum as disclosed in the United States patent, the drum must at least be of such diameter as to provide the greatest copy lengthand spaces for pulling out the photosensitive element from the drum and for winding the same into the drum, whereas the photosensitive element of the Japanese patent requires a travelling space which is 2.5 to 3.5 times the maximum copy length inasmuch as the photosensitive element is reciprocated along a plane. Thus for the movement of the photosensitive element to effect exposure and transfer, both types of photosensitive element require a very great space three-dimensionally in the former case or two-dimensionally in the latter.

SUMMARY OF THE INVENTION An object of this invention is to provide an electrophotographic copier incorporating a sheet of photosensitive element of the cassette type in which the photosensitive element pulled out from a cassette is supported on a drive mechanism in the form of an effectively endless belt that is rendered continuous by the cassette case so as to minimize the space occupied by the photosensitive element for exposure and image transfer and to thereby greatly compact the copier relative to the greatest copy area.

Another object of this invention is to permit the photosensitive element to travel over a variable distance in accordance with the copy size so as to render the photosensitive element serviceable over a prolonged period of time.

Still another object of this invention is to make it easy and simple to replace the cassette of the photosensitive element with a new one when the photosensitive element becomes unserviceable over the entire length of the sheet.

The cassette of photosensitive element according to this invention comprises a magazine for stocking a photosensitive element in the form of an elongated web or sheet and permitting a required length of the sheet to be paid out, a take-up roller for securing the leader end of the photosensitive sheet paid out from the magazine and winding up a deteriorated portion of the sheet, a cassette case housing the magazine and the take-up roller, and the sheet of photosensitive element. The photosensitive element extends from the magazine and the take-up roller in the form of a loop rendered continuous by way of the cassette.

The magazine and the take-up roller are normally locked to the cassette case against rotation. An outlet in the magazine for pulling out the photosensitive element is provided with suitable means for securing the photosensitive element thereto.

When a portion of the photosensitive element in use becomes fatigued and deteriorated, the take-up roller is driven automatically or manually to wind up the deteriorated portion into the cassette. At this time, the means for securing the photosensitive element is released to permit a required length of fresh photosensitive element to be pulled out.

The copier of this invention further includes a drive roller and a tension roller for driving the photosensitive element paid out from the cassette, and a carrier for removably supporting the cassette.

The cassette is placed on the carrier, and the loop of the photosensitive element pulled out from the cassette is reeved around the drive roller and the tension roller in the form of an endless loop which is rendered continuous by the cassette case. The drive roller and the carrier are moved back and forth during acopying operation, while the tension roller is driven by the photosensitive element defining belt.

The photosensitive element is subjected to charging, exposure and image transfer operation during its advance movement.

The photosensitive element of this invention is reciprocated within a space defined by the drive roller and the tension roller, it being unnecessary to further expand the space to drive the photosensitive element. The distance between the drive roller and the tension roller is about 1.5 times the maximum copy size. No advantages will result even if the distance is greater than twice the maximum copy size. Since the space for the travel of the photosensitive element according to this invention is almost planar, there is no need to expand the space three-dimensionally. Consequently, the copier of this invention occupies a minimal area with its height greatly reduced.

Other objects and advantages of this invention will become apparent from the following description.

BRIEF DESCRlPTlON OF THE DRAWlNGS FlG. l is a view in section showing the construction of the principal part of an embodiment of this invention; v

F IG. 2 is aperspective view schematically showing a photosensitive element cassette to be used in this invention;

FIG. 3, sections (a) and (b) are views illustrating the reciprocal movement of a photosensitive element;

FIG. 4 is a perspective view schematically showing the construction of a drive mechanism and loading means for the cassette;

FIG. is a view showing another embodiment of a drive screw for driving the cassette;

FlG. 6 is a view in section showing a structure for supporting a tension roller;

FIG. 7 is a view illustrating the means for loading the cassette; and

FIG. 8 is a view showing one mode of movement of a'cassette carrier when the cassette is loaded or unloaded.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FlG. l is a view schematically showing the construction of an embodiment of an electrophotographic copier of the latent image transfer type according to this invention. A document D is placed face down on a document table 1 made of a transparent material such as glass and is illuminated by an exposure system 2.

The exposure system 2 comprises first movable means including an iodine lamp L, a reflector S and a first reflecting mirror Ml; second movable means including a second reflecting mirror M2 and a third reflecting mirror M3; stationary means including an image-forming lens 3 and a stationary reflecting mirror M4; and an exposure slit 4 for exposing a photosensitive element P to reflected light from the surface of the document.

As detailed in Publication of Japanese Patent application No. 6647/ I964, the first movable means travels at a velocity of vwhile the second movable means travels at a velocity of v/2, so that in spite of the travel of both movable means,the light path extending from the document surface to the image-forming lens 3 by way of the first, second and third reflecting mirrors M1, M2 and M3 is maintained at a constant length. Thus the first and second movable means and the lens and reflecting mirror of the stationary means cause the reflected light from the document surface illuminated by the lamp L to pass through the slit 4 and impinge on the photosensitive element P which is moving at the same velocity v as the first movable means in synchronism therewith. The photosensitive element P is therefore exposed to an image of the document supported on the document surface. The first and second movable means reciprocate between the solid line position and the broken line position in the drawing, and the lamp L is lighted only during the forward travel to make the exposure.

The photosensitive element P in the form of an elongated web or sheet is wound up into a roll form (not shown) and accommodated in a magazine 6 within a cassette case 5. As shown in FIG. 2, the photosensitive sheet is paid out a desired length from an outlet and is secured to the outlet 6a by unillustrated suitable means which is operable electromagnetically or mechanically. The leader end of the sheet is fixed to a take-up roller 7 disposed in the cassette case 5 and normally locked against rotation.

The magazine 6 is fixedly mounted in the cassette case 5. The take-up roller 7 is biased to rotate automatically or is rotatable manually on a shaft 7a in a direction to wind up the photosensitive element P so that when a portion of the element P in use becomes worn or fatigued or deteriorated, the deteriorated portion can be taken up to pull out a fresh photosensitive portion from the magazine 6. Normally, the take-up roller 7 is locked by unillustrated'means against reverse rotation. Such mechanism will not be described in detail inasmuch as one skilled in the art can readily understand the construction.

The photosensitive element P pulled out from the magazine 6 is passed over a drive roller 8 and a tension roller 9 and is rendered substantially continuous by means of the cassette case 5 in the form of an endless belt. The drive roller 8 drives the photosensitive element P at a speed equal to that of the first movable means in timed relation to the movement of the exposure system 2. The tension roller 9 imparts tension to the photosensitive element P for example by a mechanism to be described later.

The drive roller 8 is rotated by a feed roller 10 which is in turn rotated by unillustrated drive means in normal forward and reverse directions. The feed roller 10 has a smaller diameter at its central portion than at its 0pposite ends as shown in FlG. 4 so as to be out of direct contact with the photosensitive surface of the photosensitive element P. The opposite ends of the roller 10 are in contact with the drive roller 8 to drive the same.

the reverse of the image of the document is formed as an electrostatic latent image.

The electrostatic latent image formed on the photosensitive element P is transferred while the element P advances over the curved surface of the drive roller 8. A transfer belt 12 moves along the photosensitive surface (latent image-bearing surface) of the element P as the element F moves along the curved surface of the drive roller 8. I

The transfer belt 12 is reeved around transfer rollers 13 and 14 to guide copy paper 15 withdrawn from a roll into intimate contact with the photosensitive surface and moves the paper at a speed equal to that of the photosensitive element P in the same direction. As a result, due to air discharge breakdown across the airgap between the copy paper and the photosensitive surface, a pattern of charges corresponding to the electrostatic latent image on the photosensitive surface is formed on the copy paper. The paper 15 is cut to the desired length by a cutter 16 before reaching the transfer station.

Toner is applied by a developing unit 17 to the paper 15 bearing the latent image transferred thereto to visualize the latent image. The paper is then carried on a belt 18. The visualized image is fixed by a fixing unit 19 during transport and the paper is discharged from the machine.

The construction of a copier of the latent image transfer type has been described. To construct an electrophotographic copier of the powder image transfer type, the toner may alternatively be applied directly to the photosensitive element P at a position between the exposure station and the transfer station including the transfer belt 12 to form a visual powder image prior to the transfer, followed by the transfer of the powder image. In'such construction it is already known to provide a transfer charger at the transfer station.

The operation of the photosensitive element P will now be described. The photosensitive element P reeved around the drive roller 8 and tension roller 9 in the form of an endless belt is at its start position in FIG. 3(a). In this position, the cassette case 5 is supported on a cassette carrier to be described later. The photosensitive element P is kept taut by the tension roller 9 and has one end fixed to the magazine 6 and the other end to the take-up roller 7. (The magazine and the take-up roller are both locked against rotation.)

When an unillustrated start button is depressed, the lamp L is lit and the charging unit 11 is actuated. At the same time, the first movable means and the second movable means of the exposure system 2 are initiated into travel from the solid line position to the broken line position in FIG.1 while maintaining the foregoing relation. The feed roller 10 rotates in the normal direction to rotate the drive roller 8, which in turn starts to drive the photosensitive element P in the direction of the arrow A. The transfer belt 12 is also driven at the same speed as the photosensitive element P. The cassette case 5 is moved by the carrier in the same direction and at the same speed as the photosensitive element P.

The photosensitive element P is driven by the drive roller 8 until charging, exposure and transfer are completed and is stopped upon reaching the position of FIG. 3(b) where the transfer operation is completed. Similarly, the movable means of the exposure system 2 are brought to a halt upon reaching the broken line position of FIG. '1, and the lamp L and charging unit 11 are turned off, whereupon the movable means return, along with the photosensitive element P or individually, to the solid line position in FIG. 1. The photosensitive element P is driven backward in the direction of the arrow B from the position of FIG. 3(b by thedrive roller 8 which is driven by the feed roller 10 rotating in the reverse direction. The cassette case 5 also returns together with the cassette carrier in the same direction and at the same speed as the photosensitive element.

The photosensitive element P moves back and forth along its path for each copying cycle'for repeated use. When the photosensitive surface becomes worn, the worn portion is wound up on the take-up roller 7 and a fresh photosensitive portion is withdrawn from the magazine 6. v

The cassette carrier 20 is driven, for example, by the following structure.

As shown in FIGS. 4 to 8, the cassette carrier 20 comprises a box accommodating the cassette case 5 containing the magazine 6 and the take-up roller 7. The carrier 20 is slideablysupported at one end, by means of rollers 20a on a guide rail 21 extending in parallel to the direction of advance of the photosensitive element P. At the other end of the carrier 20 there is a sleeve 20b in screw-thread engagement with drive screw 22 extending in parallelto the guide rail 21. Thus the carrier 20 is adapted to be reciprocated between the startposition and the return position. The drive screw 20 is reversibly driven by unillustrated drive means through a pulley 23 and a belt 24 to transport the carrier 20 at a speed equal to that of the photosensitive element P.

The drive screw 22 may alternatively be a screw rod 22' formed with helical reciprocation screw threads and carrying thereon a sleeve 20b with an engaging member'20c engaging with the screw thread as shown in FIG. 5, the sleeve 20bbeing secured to the carrier 20, so as to reciprocate the carrier 20 when the screw rod 22' is driven in one direction.

As shown in FIGS. 4 and 6, the tension roller 9 is supported 'on a shaft 25 provided at its opposite ends with blocks 26 which are slidably supported on guide rails 28 and 29. The guide rails 28 and 29 are C-shaped in section and secured to a frame 27. One end of the shaft 25 extends backward through a slit 27a in the frame 27 and has a fixed member 30 which is attached to an endless chain 32 reeved around sprocket wheels 31. By driving the sprockets 31, the tension roller 9 is moved parallel to the guide rails 28 and 29. i

It is seen in FIG. 4that a portion 28a of the guide rail 28 is fixed to a door 33. When the door 33 is opened, the slider 26 will be disengaged from the guide rail 28a to free one end of the tension roller 9, and when it is closed, the block 26 will'engage the guide rail 28a to support the tension roller 9.

Proximate to the other v vided microswitches M81, M52 and M83 for determin ing the position of the tension roller 9.

The tension roller 9 is brought to suitable positions and stopped under the control of the-microswitches, which therefore serve as sensing switches for determining thepositions of the tension roller 9 when the photosensitive element cassette is to be replaced by a new one and when the copy size is to be changed.

When the entire length of the photosensitive element in the cassette becomes worn and deterioratedand is no longer serviceable, the cassette will be replaced with a new one by the following procedure.

A replacement switch on an unillustrated panel of the machine frame is depressed to drive the drive screw 22 and thereby bring the cassette carrier 20 to the return position shown in FIG. 3(b) and FIG. 4. More specifically, the sprocket wheels 31 are driven to move the guide rail 29, there are protension roller 9 in the direction of the arrow A as seen in FIG. 4. This movement of the tension roller 9 permits the take-up roller 7 to rotate and thereby wind up the deteriorated portion of the photosensitive element. Upon the tension roller 9 reaching the position of FIGS. 4 and 7, the microswitch MSl detects the movement of the tension roller 9 through unillustrated means and stops the sprocket wheels 31 and therefore the roller 9.

The door 33 is then opened for the replacement of the cassette. The photosensitive element P withdrawn from the magazine 6 in the loaded new cassette is passed over the drive roller 8 and tension roller 9 and one end of the element is secured to the roller 7. The door 33 is then closed. Thus, to free one end of the tension roller 9 when the door 33 is opened facilitates the procedure of passing the photosensitive element P over the tension roller 9 for replacement of cassette.

The drive roller 8 is supported on unillustrated means. The feed roller 10 provided to drive the drive roller 8 in contact therewith may preferably be so adapted that only when driving the drive roller 8 will it be brought down into contact with the roller 8 but otherwise it is positioned above and away from the roller 8. This-can be easilyachieved for example by electromagnetic means, mechanical means or the like, so that the mechanism will not be described.

When a new cassette is completely loaded in place, an unillustrated transfer button is depressed, which closes an unillustrated replacement completion switch to drive the sprocket wheels 31 to move the tension roller 9 in the direction of the arrow B. If a small copy size is set, the microswitch M52 detects the movement of the tension roller 9, or if a large copy size is set the microswitch MS3 detects the position of the tension roller 9 to stop the sprocket wheels 31, the tension roller 9 thus being brought to the detected position corresponding to the copy size.

During the foregoing movement of the tension roller 9, the cassette carrier 20 remains stationary, with the photosensitive element P set free from the magazine 6 and permitted to be pulled out from the magazine 6. When the tension roller 9 is stopped at the detected position and locked, the unillustrated shaft of the stocker 6 is driven back a short distance to tension the photosensitive element P. The element P is then secured to the outlet. Subsequently, the drive screw 22 is driven to shift the cassette carrier 20 to its start position.

The cassette carrier 20 is disengageably mounted at its front end on a hanger 34 guided by the guide rail 21 as seen in FIG. 8. The cassette case 5 is slidable in the carrier 20 for the replacement of the cassette. One end of the drive roller 8 is supported by a holder (not shown) on the door 33. Accordingly, the opening of the door 33 frees the front ends of the drive roller 8, tension roller 9 and cassette carrier 20, permitting the forward movement of an old cassette, for replacement. To load a new cassette, the cassette is placed in the carrier 20 with the photosensitive element P pulled out to form a small loop between the magazine 6 and the take-up roller 7, whereby the photosensitive element P can be conveniently passed over the rollers 8 and 9 at the same time. if the structure is so designed that the photosensitive element wound up on the take-up roller 7 remains suitably slackened after the tension roller 9 has been shifted to the cassette replacement position (see FIGS. 4 and 7), the replacement of cassete can be conducted with extreme ease.

What is claimed is:

1. An electrophotographic copier of the transfer type comprising:

a cassette containing a storage source of a photosensitive member defining web and winding means for winding photosensitive member withdrawn from said source,

a drive roller,

a tension roller longitudinally spaced from said drive roller,

said photosensitive member extending from said source over said drive roller and said tension roller to said winding means to define with said cassette 1 an endless loop, means for rotating said drive roller in opposite forward and reverse directions for reciprocating said cassette along a longitudinal path between said drive roller and said tension roller at a speed equal to the peripheral speed of of said drive roller, 3 and means for forming an image on said photosensitive member and for transferring said image during the movement of said cassette along said path.

2. The copier as set forth in claim 1 including a shaft onwhich the tension roller is supported, a machine frame, parallel guide rails secured to said machine frame, the opposite ends of said shaft being movable in parallel along the guide rails, means for moving the shaft and tension roller, and a microswitch disposed along the path of travel of said tension roll, the moving means for the shaft being stopped when the position of the tension roller is detected by said microswitch to lock the shaft at a predetermined position.

3. The copier as set forth in claim 2 including a door providing access to the cassette, a separable section of one of the guide rails for the tension roller being fixed to said door for loading the cassette to free the front end of the tension roller shaft when the door is opened, the separated segment of the guide rail being engageable with the tension roller shaft when the door is closed.

4. The copier as set forth in claim 1, comprising a guide rail, said drive means including a drive screw, a carrier supporting the cassette, said carrier having a front end movably supported on said guide rail and the other end thereof supported on said drive screw so as to be driven at the same speed and'in the same direction as the photosensitive member when the screw is driven.

5. The copier as set forth in claim 4 including a hanger supporting the cassette carrier, said carrier having a front end movably supported on the guide rail and a rear end supported on the drive screw, the front end of the carrier being engageable with and disengageable from the hanger. 

1. An electrophotographic copier of the transfer type comprising: a cassette containing a storage source of a photosensitive member defining web and winding means for winding photosensitive member withdrawn from said source, a drive roller, a tension roller longitudinally spaced from said drive roller, said photosensitive member extending from said source over said drive roller and said tension roller to said winding means to define with said cassette an endless loop, means for rotating said drive roller in opposite forward and reverse directions for reciprocating said cassette along a longitudinal path between said drive roller and said tension roller at a speed equal to the peripheral speed of of said drive roller, and means for forming an image on said photosensitive member and for transferring said image during the movement of said cassette along said path.
 2. The copier as set forth in claim 1 including a shaft on which the tension roller is supported, a machine frame, parallel guide rails secured to said machine frame, the opposite ends of said shaft being movable in parallel along the guide rails, means for moving the shaft and tension roller, and a microswitch disposed along the path of travel of said tension roll, the moving means for the shaft being stopped when the position of the tension roller is detected by said microswitch to lock the shaft at a predetermined position.
 3. The copier as set forth in claim 2 including a door providing access to the cassette, a separable section of one of the guide rails for the tension roller being fixed to said door for loading the cassette to free the front end of the tension roller shaft when the door is opened, the separated segment of the guide rail being engageable with the tension roller shaft when the door is closed.
 4. The copier as set forth in claim 1, comprising a guide rail, said drive means including a drive screw, a carrier supporting the cassette, said carrier having a front end movably supported on said guide rail and the other end thereof supported on said drive screw so as to be driven at the same speed and in the same direction as the photosensitive member when the screw is driven.
 5. The copier as set forth in claim 4 including a hanger supporting the cassette carrier, said carrier having a front end movably supported on the guide rail and a rear end supported on the drive screw, the front end of the carrier being engageable with and disengageable from the hanger. 